A resin container, such as those represented by a bottle made of oriented polypropylene (OPP) and a bottle made of polyethylene terephthalate (PET) (PET bottle), has been used for various purposes including use for beverages, food, cosmetics, and the like. Such a container is generally manufactured by first forming a preform having a bottomed tubular shape by injection molding and compression molding a thermoplastic resin, heating the preform in a heating furnace to a temperature at which a stretching effect is exhibited, and molding the heated preform into a predetermined shape by blow molding using a die for blow molding (for example, Japanese Unexamined Application Publication No. 2003-251685).
For blow molding of the preform, liquid blow molding is a known process in which blow molding is carried out by supplying a pressurized liquid into the preform instead of pressurized air. With liquid blow molding, it is possible to simplify the production process and the configuration of the blow molding device by omitting the post forming process for filling a container with a content liquid, by using a content liquid to be filled in a container as a final product, such as beverages, cosmetics, medicine, and the like.